Engine starter gearing



Feb. 26, 1957 LL 2,782,643

ENGINE STARTER GEARING Fil ed May 31, 1955 INVENTOR- TT Y United States Patent ENGINE STARTER GEARING Donald L. Miller, Horseheads, N. Y., assignor to Bendix Aviation Corporation, Elmira Heights, N. Y., a corporation of Delaware Application May 31, 1955, Serial No. 511,828 10 Claims. (Cl. 74-6) The present invention relates to engine starter gearing and more particularly to that type in which a pinion actuated by a starting motor is moved manually or electromagnetically into mesh with a gear of the engine to be started.

As the competition between various types of starter gearing grows keener, and the performance and dimensional requirements become stricter, it is necessary to evolve simpler, smaller and more eflicient devices of this character.

It is an object of the present invention to provide a novel engine starter gearing of the above type which is efficient and reliable in operation, simple and economical in construction, and of small overall dimensions.

It is another object to provide such a device which is so constructed as to insure that the pinion is fully meshed with the engine gear before the cranking load is applied.

It is another object to provide such a device incorporating an overload slip coupling for cushioning the initial application of the torque to the engine gear.

It is another object to provide such a device in which the pinion is permitted to overrun the other elements of the shift freely when the engine starts.

The present invention is in the nature of an improvement over applicants prior Patent 2,593,167 issued April 15, 1952.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly broken away and in section of a preferred embodiment of the invention showing the parts in normal or idle position; and

Fig. 2 is a similar view of a modified form of the invention.

In Fig. 1 of the drawing there is illustrated a power shaft 1, a portion is formed with a spiral spline or high pitch multi-lea-d thread 2, and beyond the threaded portion is reduced to the diameter of the bottoms of the threads 2 as shown at 3. A pinion 4 is slidably journalled on the smooth reduced portion 3 of the power shaft for longitudinal movement into and out of engagement with a gear 5 of the engine to be started, the meshing position of the pinion being defined by an abutment ring 6 fixedly mounted on the power shaft.

Means for actuating the pinion from the power shaft is provided comprising a shifting sleeve and driving coupling member 7 threaded on the power shaft having an enlarged terminal portion 8 provided with inclined driving projections 9 arranged to cooperate with similar inclined projections 11 on a driven coupling member 12 which is slidably journalled on the smooth portion 3 of the power shaft. Coupling member 12 is also provided with overrunning clutch teeth 13 arranged to cooperate with similar teeth 14 on a flange member 15 rigidly mounted on or formed integral with the pinion 4.

A thimble 16 is rigidly mounted at one end on the terminal portion 3 of the shifting sleeve 7, and at its other end is enlarged as shown at 17 to fit loosely over the flange member 15. A barrel member 18 is arranged to surround the thimble 16 and is provided with an inwardly extending flange 19 forming a thrust bearing for the flange member 15. v

A plurality of spring washers 21 are located in the barrel member 18 and are pressed against a shoulder 22 formed by the enlargement 17 of the thimble 16 by means of a thrust washer 23 which is retained in the barrel by a terminal flange 24.

A shift collar 25 adapted to cooperate with a shifting fork 20 is slidably mounted on the sleeve 7 and is yieldingly held against a stop ring 26 by means of a compression spring 27 which bears against a shoulder 28 formed by the enlargement 8 of said sleeve.

The inclined coupling projections 9, 11 are of such depth that when they are fully meshed, the overrunning clutch teeth 13, 14 are permitted to disengage and overrun freely. A light compression spring 29, located in opposed counterbores in the adjacent portions of the sleeve 7 and driven coupling member 12, serves to normally maintain the overrunning clutch teeth 13, 14 in engagement.

In the operation of this embodiment of the invention, the assembly of the shift collar 25, sleeve 7, pinion 4 and associated parts is shifted to the right by the fork 20 which may be operated manually or electro-magnetically in conventional manner. If the teeth of the pinion 4, which is being rotated slightly by virtue of the threads 2 on the power shaft, register with the tooth spaces of the engine gear 5, the meshing movement proceeds until the pinion approaches the stop ring 6. At this time the starting switch will be closed by the shifting mechanism in the usual manner thus energizing the starting motor, not illustrated, and causing rotation of the power shaft which will be transmitted through sleeve 7, the coupling member 12 and clutch element 15 to the pinion to crank the engine.

The transmission of torque through the inclined projections 9, 11 of the sleeve and driven coupling member develops axial forces tending to wedge said sleeve and coupling member apart, but such movement is resisted by the spring washers 21 so that the pinion 4 is yieldably coupled through the sleeve 7 to the power shaft 1.

When the engine starts, the acceleration of the pinion 4 by the engine gear 5 relieves the coupling projections 9, 11 from load, thus permitting the overrunning clutch teeth 13, 14 to wedge apart against the force of the clutch spring 29, and allow the pinion to overrun. When a successful start has been secured, the parts will be withdrawn to their idle position by retraction of the shifting fork 20.

If, during the meshing movement, tooth abutment should occur between the pinion 4 and engine gear 5, the spring 27 will be compressed by the further movement of the shifting fork 2G and collar 25 until the shifting mechanism is permitted to move sufiiciently to close the starting switch in the usual man er. The starting motor then rotates the power shaft 1 to index the pinion teeth into proper registry with the engine gear, whereupon the spring 27 is effective to complete the meshing movement of the pinion 4.

It is important to note that during this meshing move ment after a condition of tooth abutment has been corrected, the threaded connection between the sleeve 7 and power shaft 1 prevents application of the cranking torque to the gearing until after it is fully meshed. Since the initial rotation of the power shaft 1 by the starting motor causes the threaded connection to assist the spring 27 to shift the pinion into its fully meshed position before the application of cranking torque thereto, the shifting move ment takes place freely and without the localized stresses on the ends of the gear teeth which are sometimes en- 3 countered when the cranking torque is assumed before the pinion is fully meshed.

The embodiment of the invention illustrated in Fig. 2 involves a further simplification of the structure shown in Fig. l by incorporating the spring washers as a part of the enclosing barrel assembly.

The coupling and clutch members, thimble and pinion are the same as in the first embodiment of the invention and are similarly numbered. In this case however a cylindrical barrel member 31 is provided in which a pair of spring washers 32, 33 are anchored in spaced parallel relation. The spring washer 32 provides a thrust bearing for the driven clutch element 15 and for the adjacent end of the thimble 16, while the spring washer 33 bears against the shoulder 22 of the thimble. It will thus be evident that the spring washers and barrel member 31 resist separation of the coupling members 7 and 12 in the same manner as the spring washers 21 and barrel member 18 in the first embodiment;, and the operation of the device is similar to that above described.

Although but two embodiments of the invention have been shown and described in detail it will be understood that changes may be made in the design and arrangement I member toward the engine gear, and including further an of the parts without departing from the spirit of the 3 invention.

I claim:

1. In an engine starter transmission a power shaft, a driving coupling member splined thereon having inclined driving surfaces formed thereon, a driven coupling member slidably journalled on the shaft and having inclined driven surfaces cooperating with the inclined surfaces on the driving coupling member, a pinion slidably journalled on the power shaft, an ove-rrunning clutch connection between the driven coupling member and pinion, a thimble surrounding the clutch and coupling members and attached at one end to the driving coupling member and yielding means external to said thimble cooperating therewith to oppose separation of the coupling members.

2. An engine starter transmission as set forth in claim 1 in which the thimble is provided with an external shoulder, and the pinion has a peripheral flange rigid there with, and said yielding means includes a barrel member with a plurality of elastic annular members therein cooperating with said shoulder and flange to resist movement of the pinion and driving coupling member away from each other.

3. An engine starter transmission as set forth in claim 1 in which the driving coupling member is spirally splined on the power shaft in the direction to cause the transmission of cranking torque to tend to move said coupling abutment on the power shaft defining the meshed position of the pinion thereon.

4. An engine starter transmission as set forth in claim 2 in which the barrel member has a flange at one end cooperating with the flange on the pinion, and a flange at the other end holding the elastic members pressed against the shoulder on said sleeve.

5. An engine starter transmission as set forth in claim 4 in which the end of the thimble abuts against the firstmentioned flange of the barrel member to thereby .keep the elastic members under initial compression.

6. An engine starter transmission as set forth in claim 5 in which the thimble is of such length as to provide space for the pinion to overrun the driven coupling member, and including further a spring urging the driven coupling member into clutching engagement with the pinion.

7. In an engine starter transmission a power shaft, 2. driving coupling member splined thereon having inclined driving surfaces on one end, a driven coupling member slidably journalled on the power shaft having inclined surfaces cooperating with those of the driving coupling member, a pinion slidably journalled on the power shaft, said driven coupling member and pinion having cooperating overrunning clutch teeth, and means for yieldably resisting separation of the coupling members including a surrounding barrel member and a pair of elastic washers anchored in the barrel, one washer having a thrust connection with the driving clutch member and the other washer having a thrust connection with the pinion.

8. An engine starter transmission as set forth in claim 7 in which the means for yieldingly resisting separation of the coupling members includes a thimble anchored to the driving coupling member having a shoulder forming a thrust bearing for one of the spring washers, while the pinion is provided with a flange forming a thrust bearing for the other spring washer.

9. An engine starter transmission as set forth in claim 8 in which the free end of said thimble normally abuts against the second-mentioned spring washer to thereby define the normal spacing of the washers.

10. An engine starter transmission as set forth in claim 9 in which the normal spacing of the washers is such as to permit the pinion to freely overrun the driven coupling member, and including further yielding means for causing engagement of the overrunning clutch teeth.

2,593,167 Miller Apr. 15, 1952 

